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    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">

        alert($(document.getElementById("testDiv"))[0]);
        // dom和jquery互换


    </script>
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<h1>dom对象转换为jquery对象</h1>
<h2>
    1.先有dom对象<br>
    2.$(dom对象)就可以转换为jquery对象<br>
</h2>

<h1>jquery对象转换为dom对象</h1>
<h2>
    1.先有jquery对象<br>
    2.jquery对象[下标]取出相应的DOM对象<br>
</h2>

<img src="../jQuery对象和dom对象互换.png">

<div id="testDiv">Atguigu is Very Good!</div>
</body>
</html>